1. Field of the Invention
This invention relates generally to fluid level sensors, and more particularly to a method and apparatus for sensing levels of insoluble fluids, including but not limited to crude oil and water, in a vessel.
2. Description of the Related Art
Devices for measuring and monitoring the fluid level in a storage vessel or tank typically are arrangements that include a sensing element or apparatus immersed in the fluid or other medium within the vessel. Many of the fluid level sensors require the fluid to be measured be in electrical contact with the gauge or require the material to be electrically conductive.
Typical devices for monitoring a fluid level in a tank or other storage vessel operate by means of an electromechanical switch that is activated by a float. The foal or floats ride on the surface of the fluid, and when the fluid reaches a predetermined level, a switch coupled to the float is activated. These types of floats and similar devices are undesirable because they are prone to sticking in either the on or off position. Other types of floats rely on a signal indicating a change in the position of the float in the vessel, which must be read each time a measurement is to be taken. This type of signal float provides a span of measurements, unlike floats coupled to a switch. However, construction of these signal floats is expensive and the floats must have a certain density in order to float on the water, but not the oil. In addition, like the floats coupled to a switch, these signal floats have a tendency of sticking. Furthermore these signal floats require specific electrical geometries, which does not allow for a realizable system of modularity.
Other known fluid level sensors utilize capacitive sensors that are directly immersed into the fluid to be measured. These capacitive sensors are subject to changes in dielectric constant. These capacitive sensors only sense the level of a single fluid and air. When these capacitive sensors are used to measure the level of multiple fluids, they determine one (1) capacitive measurement, and therefore, there are an infinite number of solutions available if there is more than one (1) unknown fluid height.
It is therefore desirable to provide a method and apparatus for sensing levels of insoluble fluids stored in a vessel.
It is further desirable to provide a method and apparatus for sensing levels of insoluble fluids that overcomes the limitations of the prior art and yet is sufficiently accurate in the measurement of the individual fluids within the storage vessel.
It is yet further desirable to provide a method and apparatus for sensing levels of insoluble fluids that requires no moving parts for sensing the level of two or more insoluble fluids.